using NPN inductive sensors for Limit

[ScorpionTDL]

Hello everyone,
I'm in the process of converting my CNC Router from Estlcam to Planet CNC.
Esltcam Required NPN Inductive sensors as limit switches. Therefore I have tose installed on the Router at the moment.

When triggered they are creating a connection between Ground and Input.
From my understanding the "Adapter for limit switch and input switch connection of Mk3 controller" only works with PNP sensors as it requires switching V+

Are there any objections to connecting NPN Sensors directly to the MK3 Board?

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[PlanetCNC]

I suppose you could do this in theory.
But I always use optocouplers in limit switches. Those long cables all over machine can be real trouble.

[ScorpionTDL]

Well Optocouplers on NPN does not really work from my understanding, they all require PNP as they all switch on voltage and not on ground on the input side.

I think I will give it a try. I have shielded cables and it worked fine with the estlcam controller.

[PlanetCNC]

Input and limit pins are internally pulled-up to 5V.
Be careful not to damage them with indicative switch higher voltage.
Anything higher that 5V on pins will damage them beyond repair.

[ScorpionTDL]

will keep it in mind

[ScorpionTDL]

quick update:
I checked the sensors I have installed on my CNC and even though being NPN they seem to have some V+ parasite power on the Out Contact if they are not triggered (the once I used on the bench did not show this behavior)
They somewhat work connected to a optocoupler but they tend to trigger spontaneously and unpredictably during rapid moves causing Estops if the estop flag is set in the configuration.
As I have some PNP sensors on the shelf I will switch to those, it will require some relabeling but better safe than sorry.

BTW: is there some way to see what event triggered the estop? I had some trouble pinning it down to the inductive sensors as it first looked es if it was caused by the error pin from my stepper motors. Having a message in the output windows telling which port triggered the estop would have been very helpful.

Best Regards
Klaus

[PlanetCNC]

I'll consider this idea.